1. Field of the Invention
The present invention relates to phosphors, and in particular relates to white light illumination device and solar cells utilizing the same.
2. Description of the Related Art
White light emitting diodes is major stream of modern illumination due to its energy-saving, low pollution, and long lifetime. The critical points of total luminous efficiency in the illumination devices are not only LED inherent brightness but also the LED phosphors.
The general commercially available white light LED is blue LED (emission wavelength of 460 nm to 480 nm) collocating yellow phosphor, thereby having worse color-rendering. In addition, the yellow light comes from the yellow phosphor excited by the blue light from the blue LED chips. Because the blue light intensity is changed by different input current, the white light will tends to yellow or blue. Furthermore, the white light color will be uneven due to blue LED chips gradually damaged by time. For improving color-rendering and luminous efficiency, the UV light emitting diode is usually adopted with red, blue, and green phosphors. Because the excitation light source is invisible light, the white light color will not be influenced by excitation light source intensity decreasing.
In U.S. Pat. No. 7,064,480 and 7,239,082 and World Pat. No. 0211211, a blue-green phosphor aluminate EuMgAl10O17 is disclosed. The phosphor is excited by an major excitation peak of 396 nm to emit a blue-green light having a major emission peak of 477 nm. However, the strongest emission intensity of this phosphor is poor.
Accordingly, the phosphor composition should be tuned to enhance its strongest emission intensity. Moreover, pure red, pure green, and pure blue phosphors are called for.